Process of and apparatus for separating



March 21, 1939. w. B FOULKE ET AL PROCESS OF AND APPARATUS FORSEPARATING Filed Aug. 51, 1936 4 Shee'r.s-Sheet 4 INVENTO RSl/z'ldziiglil oalife M W ZZZLam M4. Willy,

March 21, 1939. w. B. FOULKEKET AL PROCESS OF AND APPARATUS FORSEPARATING Filed Aug. 51, 1956 4 Sheets-Sheet l 314 JZt W 1 I I WilliamJQ. l V ZLS,

4 Sheets-Sheet 2 INVENTORS March 21, 1939. w. B. FOULKE ET AL PROCESS OFAND APPARATUS FOR SEPARATING Filed Aug. 31. 1936 March 21, 1939. w. B.FOULKE ET AL 2,150,917

PROCESS OF AND APPARATUS FOR SEPARATINC- Filed Aug. 31, 1936 4Sheets-Sheet 3 noooguocaooou In 00 000110900 9. oouo uoc o a 0 O 0 a o 0o c 0 l5 6 Q 0 o O 00 0 a 6 o a c 0 INVENTORS W lliz fifialk$ 339 WzzzzamA.

ATTORNE Patented Mar. 21, 1939 UNITED STATES PATENT OFFICE PROCESS OFAND APPARATUS FOR SEPARATING Willing B. Foulke, Media, and William A.Wills, Frackville, Pa., assignors to E. I. du Pont de Nemours & Company,Wilmington, Del., a corporation of Delaware Application August 31, 1936,Serial No. 98,821

8 Claims. (01. 209172) This invention relates to the separation of mminwhich one ingredient of the mixture will sink erals from gangue by theuse of a liquid of specific down and another ingredient of the mixturewill gravity between that of the mineral and the rise to and float onthe top. Certain phases of gangue. The invention will be described as itis the parting liquid process are affected by the applied to theseparation of coal from its indigphenomenon of altered specific gravitybut they 5 enous impurities, particularly slate, a separation aredistinguished from froth flotation. in which the process and apparatusare of par- The suggestion was made toward the middle of ticularly greatvalue, but it is to be: understood the nineteenth century that ferricchloride 1856 that this description is illustrative, not limitative. orsulfuric acid could be used as a parting liquid 10 Coal appears to havebeen known to, and to for the separation of coal and slate and attempts10 some small extent used by, the ancients. Its use were made in Englandto run the ferric chloride in China at about the year 1200 is describedby pro i p i n W h the l e b the jigs Marco Polo and about 1500 Agricoladescribed a were highly developed, the use of a parting liquid processof freeing minerals from their gangue was a bare suggestion and theattempt was a which is the direct progenitor of the jig process failurebecause of the undeveloped state of the 15 of coal cleaning, which hasthe widest use today. new process, the highly developed state of jig Inthe early days of coal mining in Europe and, separation, and theinability of experimenters to in the United states only the thick seamswere m k h p r in process a success n its lf. The mined. Hand methodswere largely in vogue and Original attempt having be n e, however, Sub-26 the need for anything except hand cleaning, or sequent inventorsworked with the suggested the most crude of mechanical methods wasunprocess and a h t o patents have n s necessary. As the thick seamswere used up, howparticularly in England and in the United States, ever,it became necessary to use thin seams and dealing With processes of theparting liquid yp seams containing veins of rock, which entailed T0 theb of 0111' knowledge and belief, hOWeVeI,

the necessity of removing the rock before the coal t y Such process thathas been need 5110- 25 could be sold. The method which came mostcessfully is One that depends upon the p g efprominently into use andwhich is today the feet of a suspension of solids such as sand or claystandard of separating coal and slate depends in Whtef- The art Withrespect teparting ed aupon the rates at which bodies of differentdensiof homogeneous Character is in industry ties sink through a liquidsuch as water. It is day as it was in the nineteenth century, un e 30known that bodies sink through a liquid at rates to compete The partingq s r w h more which are functions of their respective densities, than te 00841 and the 103588 thereof are s reat the denser sink the moreswiftly. The standard th h y w h the theoretical v n es jig washer ofthe industry takes advantage of this O more accurate Separation- TheProcesses principle, but instead of permitting the solids to emse vbeing Crude and p d, a e insink through the liquid, the liquid is forcedc pable of competing w h the highly developed through a screen on whichthe solids rest at a processes already in use in the industryy ratewhich lifts the layer of coal off the heavier a e incomplete p sses,lacking a number of slate, the coal being carried with the rush of elemnts essential to success.

liquid over a Weir and the slate being discharged It is an object ofthis invention to separate coal 40 at a lower point from the screen.Jigs are highly from slate, and other minerals from their ganguesdeveloped and are of excellent capacity and per Or o each Other, by a pWhich pe ds formance. However, the competition of oil has p the Partingeffect of a liquid 0 te ed ate driven coal producers to find means ofcleaning Spec g v y- It is another Object of this incoal which will bemore accurate in separating vention to provide efficient apparatus toaccom- 45 useful from useless lumps and producers and inplish suchseparation. Other objects of the inventors have turned their thoughts tothose procvention will be in part apparent and in part more esses ofseparation which depend upon the partfully hereinafter set forth. ingaction of a liquid having specific gravity be- The objects of theinvention are accomplished tween that of coal and that of slate. byinserting the materials to be separated into a 50 The use of a partingliquid is tobe distinmoving liquid of specific gravity intermediateguished from froth flotation. Froth flotation those of the materialswhich are to be separated, alters the apparent specific gravity of abody by by dividing middlings between the mineral and encasing it withina bubble. Parting processes, gangue according to the value: of themiddlings,

however, depend upon the use of a parting liquid by effecting theseparation under hermetical seal, 55

and by the apparatus which is more fully hereinafter described.

Figure 1 is an apparatus capable of carrying out the parting step of theprocess; Figure 1 is a vertical section through the apparatus; Figure 1ais a cross-section on the broken line la, la of Figure 1; Figure 1b is adetail, partly in section, of a preferred modification of wedge 336331;Figure 3c is a section on Figure 1b; Figure 1d is an elevational viewpartly in phantom and partly in section showing the parting apparatus;Figure la is a section of line I e, le of Figure 1d; Figure If isasection of line If, I of Figure 1d; Figure 19 is a section on line lg,lg of Figure 1; Figure 171. is a section on line Ih, In of Figure 1;Figure 12' is a section on line Ii, Ii of Figure 1; Figure 17' showsmeans for operating the preferred embodiment of Figures 1b and 1c;Figures 1k and II show a preferred method of operating the apparatus ofFigures 1b and 10.

Figures 2 and 20 do not refer to section 2 of the apparatus, but to anapparatus by means of which the efficiency of separation can beexpeditiously determined. Figure 2 is a plan view of a portion of theapparatus partly in section and Figure 2a is a cross-section on the line2-2, 2-2 of Figure'2. Figure 2b is a drawing of a scoop; Figure 2c is anenlarged detail of the hinge connection.

In Figures 1 to ll is illustrated the separating chamber. Referring tothe numerals, 3 is an enclosed tank; 3| are channel-shaped edges toopenings in the top of the tank; 32 are covers for the said openings; 33are flanges on the said covers of size to fit within the saidchannelshaped edges of the openings; 34 is a liquid which partiallyfills each said channel-shaped opening forming a hermetical seal; 35 isa vent pipe; 31 is a motor support mounted on the said tank; 38 is amotor of variable speed; 39 is a speed reducing gear of customaryconstruction comprising a chain of large and small driving and drivenwheels; 300 is a shaft running crosswise of and projecting somewhatbeyond the sides of the tank; 3M and 302 are sprocket wheels keyed tothe shaft 300 at opposite ends thereof; 303 304 are chains on oppositesides of the tank driven from the said sprocket wheels respectively;305306 are sprocket wheels mounted on the ends of shafts 301 and 308,respectively, said shafts passing through the wall of the said tank;309309 are stufling boxes which can be filled with grease from theoutside of the tank through the fittings 3); 312 are sprocket wheelskeyed to the shaft 308; 3|3 are wheels mounted on shafts 314 which arejournaled within the tank; 3l5 is a wedge-operated take-up mechanismwhereby one roller 3l3 can be moved longitudinally of the machine totake up the slack in the chain. One take-up means is placed at each endof the roller. 3l6 is a screw for operating the wedge and moving theroller; 3I1-3l1 are conveyor chains; 3! is a flight of a conveyor whichis mounted on the conveyor chains 311; 319 are perforations in theflights of the conveyor; 320 is a conveyor pan bent at the point 32| andhaving a discharge lip and chute 322; 323 is a wedgewire screen formingthe bottom of the upper portion of the conveyor pan; 324 is a section ofthe tank wall spaced considerably away from the said screen to permitliquid to make its way through the said screen and to be collected inthe said portion of the tank; 325 is a channel leading from the portion324 past the outside of the tank and connecting with the interior of thetank at 326; 321 are blow-out connections to permit the forcing of astream of Water or other liquid into the tank at that point; 328 is achute projecting through the side of the tank; 329 are dividing walls inthe chute; 339 is a back plate of a hopper; 33l are perforations in theback part of the hopper; 332 is a portion of the hopper back plate whichis inclined diagonally forward and which contains the perforations 33I3320-3320 are perforated portions of the said back plate of the hopperwhich are continued beyond the side plates thereof; 333334 are sidewalls of the said hopper, both being inclined inwardly to the degreenecessary to constrain any material entering through the chute 328 andpassing to the bottom of the tank to fall within the conveyor pan; 335is the front wall of the said chute which is constructed, in the form ofthe invention shown in Figure 3, as one piece of the front conveyor pan;336 is a section of the said wall inclined diagonally toward thereceiving end, and 331 is a portion of the said wall inclined toward thedischarge end whereby to present the. wedge face toward the chargingend; 338 is a conveyor pan; 339 is a wedge-wire screen forming thebottom of the upper portion thereof; 340 is a discharge chute attachedto or forming a part of.

the said conveyor pan; 34|-34l are sprocket wheels on the shaft 301 overwhich are trained the chains 342342 of the flight conveyor 343; 344 is abend in the said flight conveyor pan; 345 is a shaft carrying twosprocket wheels at the said bend; 346 is an extension of the conveyorpan beyond the sprocket wheels 345 and being continued downwardly toform the wedge; 34'! are means for adjusting the position of thesprocket wheels 348 which are mounted on a trunnion to carry scraperflight conveyor 343; 349 is a pan extending from side to side of themachine to catch the drip which passes through the wedge-wire screen 339and return it to the liquid in the tank; 350 is a drain at the rear andlowest point of the tank, whose bottom is preferably inclined; 35I is achamber beneath the said screen; 352 are a pipe and valve to permit the'drawing 01f of the sludge which may collect and pass through the saidscreen, the said sludge being passed through the said pipe to thesettling. tank to be hereinafter described, the continuation of the saidpipe not being shown; 353 is a chamber attached to the Wall of the tank;354 is a screw operating in a nut 355 fastened to the tank; 356 is astuffing box through which the said screw passes; 35'! is a cylinderattached to the said screw; 358 is a pipe projecting within the box 353and within the cylinder 35'! having therewith a movable fit madeliquid-tight by machining or by the use of a. satisfactory sealingmaterial; 359 is a valved pipe leading to the box 353; 360 are openingsbelow the parting liquid level connecting tank 3 and weir box 353; 360iis an opening connecting weir box and tank above the water level; 36! isan enclosed weir box on the side of the machine; 3621s a pipe weirwithin the box to control the water level. The pipe 362 is connected tothe settling tank. 363 is a pipe leading at 364 and 365 into the tank;366 is a hollow gauge within the pipe 363 and projecting thereabove.Shaft 366 of the said gauge is preferably calibrated on its outside andits hollowness is used for the insertion or withdrawal of shot or otherheavy material to its interior so that it can be standardized againstthe specific gravity of the parting liquid in the apparatus to recordcorrectly its level; 361-368 are oppositely placed hollow projections onthe sides of the apparatus; 369-310 are removable covers held on bybolts or other satisfactory means not shown to hermetically seal thoseof the said openings which are not in use; 31l-31l are flanges on thesaid projections designed to abut against and form a hermetical sealwith similarly placed flanges or similarly projecting members of thatapparatus which accomplishes the washing; 3280 is a manifold forming apart of the chute connected to a suction apparatus not shown and throughopenings 328! to the chute whereby any escaping gases may be caught; 312indicates the framework which supports the tank; the line 313 indicatesthe upper level of the liquids in the tank; the line 314 indicates theinterface of the separating liquid and the light liquid; 315 is a pipeopening into the tank whose purpose will be hereinafter described;311-311 are angle bars supported either from the members 332 and 331 orfrom the sides of the tank by bars which cover the conveyor chains andprevent them from being damaged by the descending slate; 319 is a screenextending preferably the full depth of the liquid to prevent lightmaterials from being washed back into the path of the outer conveyor.The screen stretches from wall to wall of the tank between the chute andthe outer conveyor and from a point slightly above the level of theliquid to a point just short of the lower conveyor.

This apparatus is operated to accomplish this step of the process asfollows: The valve of pipe 359 is opened and heavy liquid is admitted tothe tank through openings 360 until the level 314 is indicated on thesight gauge- 366. Water is then run into the tank through the orifices315 until the level 313 is reached. A continuous flow of water may bemaintained through the machine through the pipe 315 and the overflow362, if it is desired, or water may be added intermittently and asneeded. The height of the parting liquid in the tank is regulated by theoverflow 351. As the liquid is admitted it rises in the tank and in thebox 353 until it reaches the open top of the cylinder 351 at which pointit flows downwardly through the said overflow and through the valve andpipe 358 to the used liquid tank.- The valve in the said pipe 358 may bekept open and a continuous flow of liquid pass into the chamber throughpipe 359 and out of it through pipe 358, or the operation may be madeintermittent, control being kept by observation of the sight gauge.

The tank having been filled to the proper level with liquid, coal isdropped from the conveyor into the chute 328, passing in four streamsdown the divisions 329 by which it is distributed across the width ofthe tank. The chute 328 may be placed on either side of the machine asis indicated in Figure 16, an opening on either side being provided,that not in use being closed by a plate 316. The apparatus is started;the motors drive the two conveyors either at the same or at differentspeeds depending to some extent upon the quantity of material each hasto handle. The coal, slate, and other admixed impurities drop into thewater layer while still in the chute so that they are dispersed by thewater before reaching the parting liquid; the splash made by theirfalling is dissipated and entrained gas is removed before they leave thechute. Passing through the water layer they enter the parting liquid,whose density has been selected to be between that of coal and that ofslate. The coal floats on the surface of the parting liquid, the slatesinks down guided by the hopper 334 and, entering the conveyor pan, ispicked up by the scraper conveyor blades and carried toward thedischarge. The coal floating at the inter face of the liquids is pickedup by the conveyor 343 and carried toward and onto the conveyor pan 346.The specific gravity of the liquid is preferably chosen to be onlyslightly lower than that of the middlings. The middlings are thoseportions of the mixture which contain in one lump both slate and coal.The middlings tend to sink only slowly in the liquid whereas the slatesinks instantly and the coal floats.

Each of the conveyors acts as a pump, the effect of which can be variedby the use of scraper blades of either solid or foraminous crosssection, the number of openings in the said scraper blades beingvariable to secure pumping actions of different intensity. As the outerconveyor sweeps sunken material along its conveyor pan and up theincline toward the discharge, some of the entrained liquid tends to fallback through the orifices in the flights and that which remains issucked out of the material as it is pushed over the wedge-wire screen323. The slate is discharged through the hopper 322 into the trough 4|which forms a part of the washing apparatus elsewhere described. Thelower plate of the conveyor pan of the inner conveyor 338 is carriedwell beyond the pinion 345 and is then bent inwardly as indicated at3460 so that the floated material will be swept on without jammingbetween the flights and the pan. By carrying the conveyor pan beyond thesprocket wheels 345 the chain is enabled to bend upwardly, and enoughslack is provided therein so that when coal tends to jam the conveyor bytaking up slack it may jump and release it without damage. The conveyorflights then sweep the coal up the inclined pan, over the wedge-wiredraining screen 339, and eject it through the hopper 340 onto the trough42 which forms a portion of the washing apparatus elsewhere described.The liquid which is driven by the outer conveyor passes through thewedge-wire screen 323 downward through the chamber 324,

outside the main wall of the tank through the passage 325 and theopening 326 into the chamber which is formed in back of the partition336-331. The liquid which is entrained by the inner conveyor is swept upthe inclined conveyor pan, passes through the wedge-wire screen 339,flows down the drain board 349, and is carried back to the chamberbehind the partition 336-331. Sides 333-334 of the trough, together withthe sides of the tank, form tubes 380-38l through which liquid fromchannel 325 and the chamber beyond 336-331 may travel to the receivingend of the machine, entering again into the separating chamber throughthe orifices 33| of the plate 330. There is thus maintained a constantmotion of separating fluid and its superimposed sealing liquid from thereceiving toward the discharge end of the machine. The length of theseparating chamber, namely the distance between the plate 330 and thewedge 336-331 is such that the pieces of coal will have risen to the topof the separating liquid and the pieces of slate will have dropped tothe bottom before the wedge has been reached, but the middlings, due tothe selection of a parting liquid of only slightly lighter specificgravity, will be held in suspension, slow- 1y sinking. The middlingsrich in coal sink at a slower rate than the middlings poor in coal, dueto their different densities, and a classification of the middlingstakes place before the wedge is reached. The wedge then directs thericher middlings upward into the coal and the coal-poor middlingsdownward into the slate.

In Figures 1b and 1c is shown a means of varying the proportion ofmiddlings which is thrown into the coal and a means which materiallycontributes to the production of coal with a standard ash content. Inthose figures 346 is the bottom of the conveyor pan; 383 is a plate; 382is a hinge connecting the plate to the lip of the conveyor pan; 385 is aplate and 386 is a hinge connecting the plate 385 to plate 383; 381 arehooked-shaped members which underlap the edges of the channel irons 311for sliding movement. On the plate 383 at a point near the hinge 386there is connected a lifting rod or cable 381 which extends upwardlybetween the conveyors and the wall of the tank and through a water sealbox 388 mounted in the side of the tank to a point on the outside fromwhich it may be manipulated. 389 are rods. By pulling up on one said rodthe plate 383 will be lifted, and the plate 385 will swing toward thereceiving end of the machine, the edge 386 of the wedge will have beenraised and a greater proportion of the middlings will have been directedinto the slate, producing a coal of decreased ash content. If, on theother hand, a coal of increased ash content is desired, a second rodattached at the lower end of plate 385 and projecting through the wallof the tank in the same manner may be manipulated to draw the plate 385rearwardly and lower the angle 386. As shown in Figure 1h enough roomexists between the edge of the conveyor flights and the wall of the tankto permit the passage of a rod, and by stationing and sealing tank 388entirely outside of the wall 3 no interference between the conveyor andthe rods will be experienced. The lower end of the rod may be attachedto the wedge by a cable, as shown.

In Figures 1k and ll is shown another means of adjusting the wedge. Inthose figures 3 refers to the tank; 39039U are elongated boxes on theoutsides thereof (a corner of which is shown in dotted lines in Figurel); 391 are slots connecting the interior of the tank with the saidboxes; 392392 are links attached to the lower corners of the wedge;393393 are pins attached to the links, passing through the slots 39! andmounted in movable blocks 394; 395395 are rods attached to the saidblocks bored and screw-threaded; 396-396 are revolvable screws mountedin bearings attached to the sides of the boxes bearing at their headspinions which mesh with pinions on shaft 398 which is mounted in thesides of the tank and projects through the wall of the box and astuffing box 391; 399 is a hand wheel to turn the rod.

The operation of this apparatus is as follows: The hand wheel 399 isturned, rotating the intermeshed pinions and the rods 396 which extendor restrict the blocks 394 by reason of their screw fit with theinterior of portions 395. As the blocks 394 are moved along the boxes,they push the link 392, which being attached to the corners of the wedge385 move the wedge as indicated in part by the dotted lines of Figure110.

A brief description of the apparatus is as follows: The material to beseparated enters through the chute into the receiving end of theapparatus and is collected by the hopper which encircles the section ofthe apparatus in which the actual parting of mineral and gangue takesplace. The pumping action of the conveyors keeps the liquid incontinuous circulation from the receiving end of the parting chamber tothe discharge end thereof. The upper conveyor sweeps the floats onto theconveyor pan, and the looseness of the conveyor chains permits theconveyor flights to jump and free themselves from any particles whichtend to jam against the lip of the conveyor pan. The lower flightgathers the sinks and carries them out of the separating chamber. Themiddlings are carried by the current toward the wedge which forms thedischarge end of the separating chamber and are divided according to theproportion of slate and coal they contain, those heavy because of largequantities of slate being thrown into the refuse, and those lightbecause of usable quantities of coal being gathered in the floats. Theseparated materials are pushed by their respective conveyors overwedge-wire screens, or other suitable draining mechanism, which removethe majority of entrained liquids, and the materials themselves aredischarged by the conveyors onto the collecting pans or troughs of thescreen to be hereinafter described. -The parting liquid which passesthrough the wedgewire screens is returned along the sides of themachineand outside the separating chamber to the charging end of the machineand a continuous circulation is thus maintained. The level of heavyliquid is maintained at any desired point by the adjustable sealed weirat the end of the machine and the level of sealing fluid is maintainedby the weir box on the side of the machine. Continuous addition andremoval of liquid through the machine is thus possible, as well asintermittent additions as additions become necessary. Means are providedfor blowing out the space beneath the conveyor pans and means are alsoprovided for the removal of sludge from the bottom of the tank.

In Figures 2, 2a, and 2b is illustrated an apparatus for determining thepercentage of coal in the sinks and the percentage of slate in thefloats, in other words, for determining the ash content of the cleancoal as delivered "by the system so that the middlings may be divided tothe best advantage. In these figures 15 indicates generally a longtrough, made preferably of some chemically resistant metal; -159 arewalls which divide the trough into a series of chambers; 15l15l aretrays having foraminous bottoms 152 and preferably solid sides, theshape-of the trays conforming substantially to the shape of thecompartments of the trough. Each compartment of the trough is providedwith a tray. The trays are pivoted at one end to the trough,conveniently by a method shown in Figure 20. 153 are U-shaped membersattached by welding or otherwise to the outer edge of the tray 151; 154is a pipe or other circular member attached to or forming the edge ofthe trough 15; 155 are bolts passing through the ends of U-shapedmembers 153; 156 are handles attached to the lip of the tray 15!opposite to the pivot; 151 are stops so placed that they contact theedge of the said trays and prevent their making contact with the bottomof the trough 15; 158 are pipes and valves leading to each compartmentfor drainage purposes; 159 are stop bars placed approximately midway ofand running the length of the sides of the trays; 160 is a scoop havinga foraminous bottom 16l and a handle 162; 163 are means for supportingthe trough; 164 is a shelf running lengthwise of and before the troughand having an edge 165 to prevent the escape of liquid and. a drainagechannel 166 and pipe 161 for such liquid; 168 is a screen to prevent theescape of solids down the drain. H is a means, such as a steam line, toregulate the temperature of the bath.

In normal operation the apparatus will have possibly ten compartments.Each compartment will be filled to equal depth with a liquid. 169 showsa liquid level. For example, the first compartment will contain a liquidof specific gravity 1.9; the next will have a specific gravity of 1.85;the next 1.8; the next 1.78; the next 1.76; etc., the specific gravitiesbeing chosen to give the maximum information with the particular coal orother mineral being treated in the process at the moment. A sample istaken, for instance, of the coal which is discharged from thewatersealed conveyor and a weighed portion thereof is put into the firstcompartment. Assuming that the specific gravity of the compartment hasbeen correctly chosen for the first test, a considerable portion of thecharge will sink and the remainder will float. The operator then takesscoop I60, inserts its nose within the tray, as shown in Figure 2a,slides it across the runners which are at equal depth in eachcompartment and withdraws the floats. The liquid is allowed to drainback through holes Hil in the foraminous bottom of the scoop and thefloats are placed in the next tank, whose specific gravity is somewhatlower. This procedure is continued until the sample has been dividedaccording to specific gravities. By pulling on the handle 156 the trays15! may be pivoted about pipes 154, draining through holes 152 back intothe trough I and the sunken material may be dumped into a pan or othersuitable means placed on the table 164.

The system is first calibrated by making ash determinations with theparticular type of coal which is being separated, a determination beingfirst made of the specific gravity of the incoming matter to determinethe specific gravity of the parting liquid to be used in the tank 3.After operation has commenced, samples are taken of both the sinks andthe floats and ash determinations are run to calibrate the system.Thereafter, determination of specilc gravities is made by plottingsubsequent tests against the control. In this way the coal content ofthe slate and the slate content of the coal may be determined and fromthe information obtained adjustment made to vary the percentage of slatein the coal as hereinbefore described. In each instance there will begiven an accurate check on the distribution of middlings since it willbe understood that, if the specific gravities range between that inwhich pure coal alone will float and that in which slate alone willsink, the specific gravities of the samples which sink in succeedingbaths will be in direct relation to their respective quantities of coaland stone. Zinc chloride solution is a satisfactory agent for use inthis apparatus because it can be easily diluted to precise specificgravities, but any other satisfactory liquid may be used. Havingdetermined the distribution of the middlings as actually distributed bythe apparatus, a prompt change can be made in the setting of theapparatus so that another and more favorable distribution can be made ifsuch is desired.

The apparatus which has been described offers an excellent method ofaccomplishing the process.

In the parting step of the process the liquid used is preferably organicand of the halogenated hydrocarbon type. However, the process is notlimited to such agents since any separating agent which has properspecific gravity and is properly inert to the materials which are to beseparated may be used. The factors which are desirable are that amaterial shall have high boiling point in order that there shall be lowvapor pressure at working temperatures, low melting point in order thata material may be liquid at working temperatures and the expense ofkeeping the compound fiuid by heat avoided, low solubility in water inorder that the parting liquid may not become contaminated with thesealing liquid and may not be carried out on the separated material,stability under the conditions of operation including stability toagents, air, light, and heat, low hydrolyzing capacity, low toxicity inorder to avoid injury to operators when the apparatus is cleaned, lowviscosity, and low cost. Among the compounds which have been founduseful are the following:

Pentachloropropane, 3,4 dibromo 2,2 dimethyl butane, iodobutane,hexachloropropane, 1 chloro 3 bromopropane, 1 bromo 2,3 dichloron-butane, 1 iodobutane, 1 chloro 1 bromoethane, 1,3 dibromo 2,2 dimethylpropane, 2,4 dibromopentane, pentachloroethane, 2,3 dibromopentane, 1,2dibromo 2 methyl butane, 1 chloro 2 bromoethane, 2iodopropane, 1,5dibromopentane, 1,4 dibromopentane, heptachloropropane, 1,2dibromopentane, 1 iodoheptane, 2 chloro 1 iodobutane, 1,1 chloro 1bromoethane, 1,1 dibromo 2,2 methyl propane, 1,4,7 tribromoheptane,1,1,1 trichloro 2 bromopropane, 2,2 dibromopropane, 1,2 dibromo 2 methylpropane, 1,3 dibromobutane, 1,4 dibromobutane, 1,2 dibromobutane, 1,3dibromo 2 methyl propane, 2,3 dibromobutane, 2,2,2 trichlo-ro 1bromoethane, 2 chloro 1 iodopropane, 3 chloro 1 iodopropane, 3 chloro1,2 dibromobutane, iodoethane, 2 fiuoro 1,1,2,2 tetrabromoethane,dichlorobromomethane, 1,2 dibromopropane, 1 chloro 2,3 dibromobutane,1,3 dibromopro-pane, chlorobromomethane, tribromo 2 methyl pentane, 3chloro, 1,2 dibromopropane, dichloriodopropane, 1,6 diiodohexane,trichlorobromomethane, 1 chloro 1 iodoethane, 2 chloro 1,2 bromopropane,1,3 dichloro 1,2 dibromopropane, fiuoro 1,2 dibromopropane, 1,1dibromoethane, 2,3 dichloro-1,2 dibromopropane, 2 fiuoro 1,1 dichloro1,2 dibromoethane, 1 chloro-1,1 dibromoethane, 2 chloro 1 iodoethane,1,2,2 tribromobutane, 1,2,3 tribromobutane, 1,1,2 bromobutane, 1,2dibromoethane, 1,5 diiodopentane, 2 bromo 2 iodopropane, 2,2 dichloro 1iodoethane, 1,2,3 tribromobutane, 2,2 difiuoro 1 iodoethane, 1,1difiuoro 1,2 dibromoethane, 1,1,2 trifluoro 1,2 dibromoethane, 1 fiuoro1,2 dibromoethane, 2 chloro-1,2 dibromoethane, methyl iodide, 1,1dichlor 1,2 dibromoethane, 1,2 dichloro 1,2 dibromoethane, 2,2,2trichloro 1,2 dibromoethane, 1,3 iodobutane, 1,4 iodobutane, 2,2difiuoro 1,1 dibromoethane, 1,2,2 tribromopropane, 1,4,7 triiodoheptane,1,1,2 tribromopropane, trichloro iodomethane, 2,2 dichloro, 1,1dibromoethane, 3 chloro 1,2,2-tribromopropane, dibromo dichloromethane,1,2,3 tribromopropane, 1,2,2 trichloro, 1,1,2 tribromoethane, dibromochloromethane, 2,2 diiodopropane, chloro iodomethane, dichloroiodomethane, dichloro tribromobutane, 1,2 diodopropane, 1

bromo 1 iodoethane, 2 bromo 1 iodoethane, 1,1,4,4

1,1,2,3 tetrabromopropane, 1,1 diiodoethane, bromoform, hexabromobutane,1,1,1,2 tetrabromoethane, iodobromomethane, 1,1,2,2 tetrabromopropane,l,1,2,2 tetrabromoethane, 1,1,2,2,3 pentabromopropane, diiodochloromethane, pentabromoethane, methylene iodide, 1 chloro 1,1,2,2tetrabromoethane, perchlorethylene, 1,3 dibromopentene-2, 1,1,2,3,3,3hexachloropropene-l, 2- iodopropene-l, 2 chloro 1 bromoethene,2-iodopropene-l, 1,3 dibromo 2 methylpropene-l, 1,2 dichloro 1bromoethene, 1,2 dibromobutene-l, 2,2 dichloro 1 bromoethene, 2-chloro3- iodopropene-l, 1 chloro 3 iodopropene-l, 1,2 dibromopropene-l, 3iodopropine-l, 1,1,2 chloro 1 bromoethene, 1 iodopropine-l, 1,3dibromopropene-l, 1,3 dibromopropine-l, 2 chloro 11' iodoethene, 1chloro 1,2 dibromoethene, 1,2 dibromethene, 2 fluoro 1,1 dibromoethene,1,2 difiuoro 1,2 dibromoethene 1,2 dichloro 1,2 dibromoethene, 1,2,3tribromopropene-l, 1,2 diiodopropene-1, 2 bromo 1 iodoethene, fluorotribromoethylene, tribromoethylene, 2,2 dibromo 1 iodoethene, 1,2iodoethene, iodocyclohexane, 1,2 dibromocyclohexane, 3,4 dibromo, 1,2dimethylbenzene, 3,4 dibromotoluene, 2,6 dibromotoluene, 2,5dibromotoluene, iodobenzene, 1 iodo 2 chlorobenzene, 1,3

dibromobenzene, 1,2 dibromobenzene, trichlorethylene, 4 chlorethane, andcarbon tetrachloride.

The list has been mainly directed to halogenated hydrocarbons but it isto be understood that any liquid having the desirable qualities setforth above can be used so far as the mere separating step is concerned.

Kerosene, benzene and naphthalene and other hydrocarbons, particularlythose of low boiling point and vapor pressure can be used as diluents toalter the specific gravity of parting liquids.

The specific gravity of the parting liquid used will be between thespecific gravities of the minera] and gangue which are to be separated.The separating liquid within the tank will be covered by a sheet ofwater or other liquid inert thereto which will serve the purpose ofpreventing evaporation of the liquid and of rejecting parting liquidwhich gathers on the floating material. The liquids may be so arrangedas to fill the whole tank or to fill only a portion of the tank.

It is advisable to design the chamber in which the separating actuallyoccurs with particular reference to the mineral which is to be treated.For example, if a finely divided iron is to be separated from itsgangue, a longer chamber would be required in order to give all the fineparticles an opportunity to respond to the parting action of the liquid.On the other hand, in those cases where no rafting of the particles isobservable and separation is quickly and completely carried out, a shortchamber may be used. Another method of accomplishing this variation isto vary the speed at which the liquid within the separating chambertravels, thereby varying the length of time which the material is allowed to separate. 7

The parting liquid can be of one liquid or it can be a mixture ofcompletely miscible liquids of difierent specific gravities. Thus, amixture of C2H2BR4 and 02112014 will give a range of specific gravitiesfrom 2.39 to 1.59. This principle can be availed of to adjust thespecific gravity of the liquid to one in which the middlings will sinkat a rate most favorable for separation by the apparatus. This selectionof specific gravity may be availed of to secure particular separation ofthe middlings in a machine provided with an immovable wedge.

The velocity with which the conveyors travel in this apparatusdetermines the point to which the middlings will have sunk at the momentthey contact the wedge. Thus, by speeding up or slowing down theconveyors the velocity of the liquid can be increased and a variation inthe slate containing middlings included with the coal accomplished. Byspeeding up the conveyors the liquid will travel faster, the middlingswill not have sunk so far and a wider percentage of lowcoal middlings beincorporated with the coal. By slowing down the conveyors the partingliquid will travel more slowly and only the richer coal middlings beincorporated with the coal.

A third method of varying the slate content of the coal and the coalcontent of the slate is by adjusting the point of the Wedge up or down.Means for doing this have been described in the specification.

These three methods of dividing the middlings may be used separately,with one another, or all together and when so used give the verygreatest flexibility to the system.

This description has been more less specifically directed to theseparation of coal from its indigenous impurities. The process is notlimited to coal, however, and it is applicable to the separation ofminerals in general, although it can be readily understood, as elsewhereherein pointed out, that to secure the best results with a particularmineral the speed of the liquid medium, the density of the partingliquid, and the length of the separating chamber may be varied.Substantially all minerals are obtained in their native condition inadmixture with indigenous impurities. In some cases the mineral is theheavier and the gangue the lighter. In such case the gangue will fioaton the surface of the parting liquid and the mineral will sink to thebottom and be carried out by the lower conveyors. In other cases, as inthe case of coal, the reverse is true. The design of the conveyor systemmay advantageously be altered to accommodate the amounts of mineral andgangue which is to be expected with a particular process. Anothervariation which must be considered by the engineer in treating differentminerals is that the specific gravities of the minerals themselves vary.Thus, anglesite varies from 6.1 to 6.4; anthracite coal varies from 1.3to 1.7 and bituminous coal varies from 1.1 to 1.5. Among the mineralswhich can be separated from their gangues by this process are thefollowing: asbestos, bituminous coal, anthracite coal, chrysocolla,garnerite, quartz, feldspar, black diamond, mica, fluorite, wad,siderite, calamine, rhodochrosite, diamond (gem grade), cyanite,limonite, azurite, psilomelane, malachite, garnet, corundum, sphalerite,willemite, chalcopyrite, smithsonite, witherite, rutile, stannite,

chromite, barite, tetrahedrite, ilmenite, energite, pyrrhotite,covellite, pentlandite, molybdenite,

braunite, pyrolusite, bornite, hematite, pyrite,

magnetite, franklinite, millerite, zincite, chalcocite, cuprite,scheelite, anglesite, vanadate (lead), cerussite, heubnerite,cassiterite, wolframite, galena, iron, niccolite, ferberite, cinnabar,copper (native), silver, platinum, and gold.

An advantage of the invention is the rapidity with which the apparatusand process can be operated with satisfactory results. A unit havingonly four square feet of separating surface was tested for speed andsatisfactorily separated tons per hour, its capacity being then limitedby the capacity of the conveyors which were working at utmost capacityand could not handle a higher rate. The ultimate capacity of the systemis at present unknown. With normal comparatively leisurely speeds ofoperation its capacity is ten times that of any previous system,comparison being made on a basis of separating surface areas.

Coal may be prepared by this process with any degree of ash content theoperator desires, something which no previous process has everaccomplished. Heretofore systems of coal cleaning had made a roughdivision between coal and slate but the percentage of coal in the slateand the percentage of slate in the coal varied from minute to minute.The idea of producing coal of standard ash content was a desideratumwithout a means of obtaining it. 85% eiiiciency has been considered goodfor coal cleaning processes and many of the mountainous waste banksfound in the coal regions contain 15% to 35%. of usable fuel. By ourinvention these waste piles may be reclaimed. No previous method wascapable of economically extracting the coal from such waste piles.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that we do not limit ourselves to the specific embodimentsthereof except as defined in the appended claims.

We claim:

1. Apparatus for the classification of minerals of difierent specificgravities which comprises a tank, means to admit liquid to the tank,means to maintain the level of the liquid, a separating chamber havingreceiving and discharge ends, said separating chamber being at least inpart below the liquid level and having an opening in the lower partthereof, means to admit a second liquid above the level of the first,means for admitting solids to the separating chamber at the receivingend thereof beneath the level of the upper liquid, conveying means towithdraw sinking solids from beneath the separating chamber, means todraw from the said solids the entrained liquid, means to discharge thesaid solids from the apparatus, conveying means to remove floatingmaterials from the said lower liquid, means to draw off entrained liquidfrom the said floated solids, means to discharge the said floated solidsfrom the apparatus, said conveying means moving the liquids continuouslyfrom the receiving to the discharge end of the separating chamber, meansto return the liquids to said separating chamber adjacent saidreceivingend, means to drive the said conveying means, and means fordraining said tank.

2. Apparatus for the classification of minerals of different specificgravities which comprises a tank, means to admit liquid to the tank,means to maintain the level of the liquid, a separating chamber havingreceiving and discharge ends, said separating chamber being at least inpart below the liquid level and having an opening in the lower partthereof, means to admit a second liquid above the level of the first,means for admitting solids to the separating chamber, beneath the levelof the upper liquid conveying means to withdraw sunken solids frombeneath the separating chamber, conveying means to collect materialsfloating in and withdraw them from the said lower liquid, means to drawoff entrained liquid from the said Withdrawn solids,

ratus, said conveying means operating to move the said liquidscontinuously from the receiving to the discharge end of the separatingchamber, and means permitting the return of the liquids back to saidseparating chamber adjacent said receiving end.

3. In an apparatus for effecting gravity classification of dividedsolids containing parts of mixed composition, a moving stream of liquidof gravity intermediate the gravities of some of said solids and capableof temporarily suspending some of said parts of mixed composition, anoverlying second body of liquid, a channel for confining said stream ofliquid to a predetermined path, a wedge-shaped element positioned insaid channel and immersed in said moving stream of liquid, saidwedge-shaped means serving to effect horizontal classification of themixed composition materials suspended by said moving stream of liquid.

4. The process of classifying a mass containing separate constituentsand pieces of mixed constitution which comprises inserting the said massin a moving stream of liquid having a specific gravity more than onesaid constituent, slightly lighter than the average specific gravity ofthe pieces of mixed constitution, and less than the heavy constituent,transporting the floating pieces and pieces of mixed constitution in themoving liquid until a gravity classification has been effected, andgathering pieces of mixed constitution having a useful quantity of thefloating ,constituent into the floating constituent, and

gathering pieces of mixed constitution having a larger percentage of thelower constituent into the sunken constituent by horizontally splittingthe stream that carries them.

5. In the beneficiation of minerals the process of isolating the betterfrom the poorer middlings which comprises inserting a crushed, roughlysized mass containing the minerals and middlings in a moving stream ofliquid having a specific gravity slightly lighter than the averagespecific gravity of the middling mass, transporting the middlings in thesaid moving liquid until a gravity classification has been effected, andseparating the better middlings from the poorer middlings bymechanically forcing the moving better middlings in the upper zone ofthe stream and separating the said zone from the remainder of thestream.

6. In the beneficiation of coal according to the process defined inclaim the steps of determining the ash content of the materialswithdrawn from the top zone of the stream and the ash content of thematerials withdrawn from the bottom zone of the stream, and including inthe upper zone of the stream all the solids above a certain levelthereof, said level being selected to include within the said upper zonea selected quantity of ash producing ingredients whereby to produce acombustible product of uniform ash content.

7. A channel, means to conduit liquid from one to the other end thereof,means to fill said channel with liquid, upper and lower conveyorsoperable in the same direction at a speed which will permit gravityclassification of middlings in the said channel, means to admit crushedminerals to said channel in the range of operation of the conveyors, andmeans to separate the material moved by the upper conveyors from thatmoved by the lower conveyors comprising adjustable means between theconveyors horizontally partitioning the stream of liquid, and meansassociated with the said adjustable means to direct the classifiedlighter middlings into the zone of the upper conveyor, and theclassified heavier middlings into the zone of the lower conveyor.

8. Apparatus for the separation of solids of different specificgravities which comprises a tank, means to admit liquid to the tank,means to maintain the level of the liquid, a separating chamber havingreceiving and discharge ends, said separating chamber being at least inpart below the liquid level and having an opening in the lower partthereof, means to admit a second liquid above the level of the first,means for admitting solids to the separating chamber, conveying meansmoving in one direction along the channel to withdraw sinking solidsfrom the lower part of the separating chamber, conveying means operatingalong the channel in the same direction as said conveying means tocollect and withdraw materials floating in the said lower 5 the impulseof the conveyors.

WILLING B. FOULKE. WILLIAM A. WILLS.

' CERTIFICATE OF CORRECTION. Patent No. 2,150,917. March 21, 1959.

I WILLING B. FOULKE, ET AL.

It is hereby certified that error appears the printed specification ofthe aho'kie numbered patent requiring correction as follows:- Page 2,first column, line 9, for "5c" read 10; page 5, first column, line h5,for "specilc" read specific; same page, second column, line 5?,for "1,2"read 1,1; line 68, for "methylane" read methylene; page 6, first column,line 7, for "1,5" read 2,5; line 9, for "2-iodo-" read 5-iodo-; line 17,for "dibromethene" read dibromoethene; page 7, first column, lines 67and 68, claim 2, strike out the words "beneath the level of the upperliquid"; same page, second column, line 62, claim 7, for the word"conduit" read conduct; and that the said Letters Patent should be readwith this correction therein that the M 1 same may confo'rm to therecord of the case in the Patent Office.

Signed and sealed this 20th dayjof June A. D. 1959.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

